Energy absorbing structures

ABSTRACT

Fastener units (FIGS. 1 and 2) include drawable rods having drawable portions and heads of the same diameter and wedging units tensioning the rods. Another fastener unit (FIG. 3) has a die, a threaded head and a nut. A further fastener unit (FIG. 4) has a combined die and threaded plug connected by a frangible portion. Further fastener units (FIGS. 5 to 12) include capscrewlike drawable rods. Another fastener unit (FIGS. 13 and 14) has a drawable rectangular bar. A further fastener unit (FIGS. 15 and 16) has a die holder into which a drawing die strip is inserted from one side. Another fastener unit (FIGS. 17 and 18) includes a drawable spacer sleeve. Other fastener units (FIGS. 19 to 24) include splittable spacer sleeves. Another fastener structure (FIGS. 25 to 28) has extrudable tubes mounting a bumper on a vehicle frame. Another fastener unit (FIGS. 29 and 30) includes a drawing die and a rod bender for absorbing energy. A further fastener unit (FIGS. 31 to 33) has a drawable rod with two tapered drawable portions.

[4 1 Feb. 6, 1973 1 1 ENERGY ABSORBING STRUCTURES [75] Inventor:

[73] Assignee: Omark Industries, Inc., Portland,

Oreg.

[22] Filed: Sept. 18, 1970 [21] Appl. No.: 73,548

Myron D. Tupper, Portland, Oreg.

[52] US. Cl. ..85/1 R, 188/1 C, 287/18936 F, 293/89 [51] Int. Cl ..Fl6b31/02, Fl6d 19/00, Fl6d 63/00 [58] Field of Search ..85/1 R, IT, 61, 62,77, 78, 85/73, 74; 285/2, 93; 297/216; 72/267, 277, 291; 188/1 C;180/91; 293/84, 89

[56] References Cited UNITED STATES PATENTS FOREIGN PATENTS ORAPPLICATIONS 993,611 6/1965 Great Britain ..85/77 998,535 7/1965 GreatBritain ..188/1 C Primary ExaminerRamon S. Britts Attorney-Buckhorn,Blore, Klarquist and Sparkman [57] ABSTRACT Fastener units (FIGS. 1 and2) include drawable rods having drawable portions and heads of the samediameter and wedging units tensioning the rods. Another fastener unit(FIG. 3) has a die, a threaded head and a nut. A further fastener unit(FIG. 4) has a combined die and threaded plug connected by a frangibleportion. Further fastener units (FIGS. 5 to 12) include capscrew-likedrawable rods. Another fastener unit (FIGS. 13 and 14) has a drawablerectangular bar. A further fastener unit (FIGS. 15 and 16) has a dieholder into which a drawing die strip is inserted from one side. Anotherfastener unit (FIGS. 17 and 18) includes a drawable spacer sleeve. Otherfastener units (FIGS. 19 to 24) include splittable spacer sleeves.Another fastener structure (FIGS. 25 to 28) has extrudable tubesmounting a bumper on a vehicle frame. Another fastener unit (FIGS. 29and 30) includes a drawing die and a rod bender for absorbing energy. Afurther fastener unit (FIGS. 31 to 33) has a drawable rod with twotapered drawable portions.

2 Claims, 33 Drawing Figures PATEHTED FEB 6 I975 SHEET 2 [IF 6 TUPPERNTOR T & SPARKMAN TORNEYS MYRON D.

I INVE BUCKHORN, BLORE, KLARQUIS AT PAIENIEBFEB' a ma 3. 714.859

SHEET 30F 6 7 FIG. I l FIG. I2 384 39 386 39: 393

FIG. I3

MYRON D. TU ER INVENTO BUCKHORN, BLORE, KLARQUIST & SPARKMAN ATTORNEYSPATENTEUFEB 61975 3,714,859

SHEET R [If 6 FIG. l8

5.5 52 504 FIG. 24

MYRQN D. TUPPER INVENTOR BUCKHORN, BLORE, KLARQUIST & SPARKMAN ATTORNEYSPATENTEDFEB 6 I975 SHEET 5 OF 6 FIG. 27

MYRON D. TUPPER INVENTOR BUCKHORN, BLORE, KLARQUIST & SPARKMAN ATTORNEYSPATENTEDFEB 6 I975 SHEET 8 0F 6 mm 0E I'III hon MYRON D, TUPPER INVENTORBUCKHORN, BLORE, KLAROUIST 8. SPARKMAN ATTORNEYS ENERGY ABSORBINGSTRUCTURES DESCRIPTION This invention relates to improved energyabsorbing structures and more particularly to energy absorbing fastenerstructures.

An object of the invention is to provide improved energy absorbingstructures.

Another object of the invention is to provide energy absorbing drawablefastener structures.

A further object of the invention is to provide simple, inexpensiveenergy absorbing structures of low weight and high energy absorbingcapacity.

Another object of the invention is to provide improved energy absorbingstructures which can be used as bolts to fasten members together inclose or abutting proximity.

Another object of the invention is to provide energy absorbing unitshaving wedging, slack takeup structures.

Another object of the invention is to provide an easily manufactureddrawable rod having a shank and a head and a drawable portion of thesame diameter.

Another object of the invention is to provide an energy absorbingfastener unit in which a die is secured to a threaded plug by afrangible portion.

Another object of the invention is to provide capscrew-like drawablerods pressing against dies to secure members together.

. Another object of the invention is to provide energy absorbingfasteners in which drawing dies draw drawable members to rectangularshapes.

Another object of the invention is to provide an energy absorbingfastening unit in which a drawing die initially in the form of a bar isbent into a collar as it is inserted into a slot in a die holder.

Another object of the invention is to provide an extrudable sleeve heldby a bolt against a reducing die.

. Another object of the invention is to provide energy absorbingfastener units including sleeves held against sleeve expanding orsplitting members.

Another object of the invention is to provide an energy absorbingfastener structure in which extrudable tubes carrying a vehicle bumperextend through extruding dies mounted on a vehicle frame and are securedto the frame.

Another object of the invention is to provide an energy absorbingfastener structure in which a drawable rod is drawn through a bendingdie and a drawing die.

Another object of the invention is to provide an energy absorbingfastener structure having a drawable rod having two drawable portions atopposite ends of a shank thereof.

Another object of the invention is to provide an ener-' FIG. 4 is asectional view of an energy absorbing fastener unit forming an alternateembodiment of the invention;

FIG. 5 is a fragmentary, partially sectional view of an energy absorbingfastener unit forming an alternate embodiment of the invention;

FIG. 6 is an end view of the fastener unit of FIG. 5;

FIG. 7 is a fragmentary, partially sectional view of an energy absorbingfastener unit forming an alternate embodiment of the invention;

FIG. 8 is an end view of the fastener unit of FIG. 7;

FIG. 9 is a fragmentary, partially sectional view of an energy absorbingfastener unit forming an alternate embodiment of the invention;

FIG. 10 is an end view of the fastener unit'of FIG. 9;

FIG. 11 is a fragmentary, partially sectional view of an energyabsorbing fastener unit forming an alternate embodiment of theinvention;

FIG. 12 is a sectional view taken along line 12-12 of FIG. 1 1;

FIG. 13 is a fragmentary, partially sectional view of an energyabsorbing fastener unit forming an alternate embodiment of theinvention;

FIG. 14 is a fragmentary, end view taken along line 14-14 of FIG. 13;

FIG. 15 is a fragmentary, partially sectional view of an energyabsorbing fastener unit forming an alternate embodiment of theinvention;

FIG. 16 is a fragmentary, sectional view taken along line 16-16 of FIG.15;

FIG. 17 is a fragmentary, partially sectional view of an energyabsorbing fastener unit forming an alternate embodiment of theinvention;

FIG. 18 is a fragmentary, end view taken along line 18-18 of FIG. 17;

FIG. 19 is a fragmentary, partially sectional view of an energyabsorbing fastener unit forming an alternate embodiment of theinvention;

FIG. 20 is a fragmentary, end view taken along line 20-20 of FIG. 19;

FIG. 21 is a fragmentary, partially sectional view of an energyabsorbing fastener unit forming an alternate embodiment of theinvention;

FIG. 22 is a fragmentary, end view taken along line 22-22 ofFlG. 21;

FIG. 23 is a fragmentary, partially sectional view of an energyabsorbing fastener unit forming an alternate embodiment of theinvention;

FIG. 24 is a fragmentary, end view taken along line 24-24 of FIG. 23;

FIG. 25 is a fragmentary, top plan view of a vehicle structure includingenergy absorbing fastener units and forming an alternate embodiment ofthe invention;

FIG. 26 is an enlarged, fragmentary, vertical sectional view taken alongline 26-26 of FIG. 25;

.FIG. 27 is an enlarged, fragmentary, horizontal sectional view takenalong line 27-27 of FIG. 26;

FIG. 28 is an enlarged, fragmentary, vertical sectional view taken alongline 28-28 of FIG. 27;

FIG. 29 is a fragmentary, partially sectional view of an energyabsorbing fastener structure forming an alternate embodiment of theinvention;

FIG. 30 is a vertical, sectional view taken along line 30-30 of FIG. 29;

FIG. 31 is a fragmentary side elevation view of a vehicle structureforming an alternate embodiment of the invention;

FIG. 32 is a top plan view taken along line 3232 of FIG. 31; and

FIG. 33 is an enlarged vertical, sectional view taken along line 3333 ofFIG. 31.

EMBODIMENT OF FIG. 1

Referring now in detail to the drawings, there is shown in FIG. 1 anenergy absorbing fastener unit 40 forming one embodiment of theinvention, serving to hold plate-like members 41 and 42 together forseparating forces not greater than a predetermined minimum force and todraw a drawable portion 47 of a drawable rod 44 when a force higher thanthat predetermined minimum force occurs. The rod has a shank 46, atapered transition portion 51 and a threaded head 45 of a diameternominally the same as that of the drawable portion 47 and joined to thehead by a shouldered or abrupt, transition or filleted portion 52. Acupped nut 54 having a frustoconical counterbore 56 is screwed onto thehead 45 to wedge a split locking collar 58 tightly against the rod andagainst the head 45 to clamp the members 41 and 42 tightly between thecollar and a split drawing die 60, the halves of which are held togetherby a ring 62 bonded to the die 60. The collar 58 has a frustoconicalexterior surface 64 and an end surface 66 complementary to the steeplysloping transition portion 52. The plate members 41 and 42 have alignedbores 68 and 70 of a diameter slightly larger than that of the head 45and the drawable portion 47.

Since the head 45 is of the same diameter as the drawable portion, therod 44 can be inexpensively made by turning the shank 46 and portions 51and 52 and rolling or otherwise forming the threads on the head. Thismakes the rod, which is the only part usually destroyed, for reuse bythe drawing of the rod, easily replaceable. The rod-44 may be of ahardened steel, preferably of uniform hardness throughout, the drawableportion 47 being sufficiently soft to be drawn, the hardness preferablybeing from about 50 to about 55 on the Rockwell C scale. The rod may beof 4140 steel or one of the commercially available steels like the 4l40but more easily machined. The rod is preferably heat treated to providea tensile strength of from 190,000 to 200,000 pounds per square inch,uniform throughout the rod. The rod also may be of other drawablematerial, such a s for example, copper, aluminum or of a harder steel.

The fastener unit 40 holds the members 41 and 42 together until apredetermined force higher than usually encountered, is exerted on themembers to separate them. Then the portion 47 of the rod is drawn by thedie and absorbs the force which is separating the members.

The energy absorbing capacity of the unit 40 is high relative to theweight and size thereof. This is made possible by having the strength ofthe head and the nut and the die each as great as the tensile strengthof the shank. The ratio of the drawing force required to draw the rod tothe tensile strength of the shank is designated as the stress ratio" ofthe unit, and the unit has a high stress ratio. The energy absorption isdue primarily to the internal deformation of the rod as it is drawn butalso includes the friction between the die and the surface of thetransition portion 51 whichis converted into heat. To provide a highstress ratio the difference in the diameters of the drawable portion 47and the shank 46 is so chosen that the resistance to pulling thedrawable portion through the die (the drawing and friction forces) isnot substantially less than 40 percent of the tensile strength of theshank and is not substantially greater than percent of that tensilestrength of the shank. The head 45 has such diameter and such lengththat it does not fail during the drawing of the portion 47, the strengthof the head preferably being at least as great as the tensile strengthof the shank. The fillet 52 is provided at the juncture of the head andthe shank to prevent stress concentration. The diameter and length ofthe nut and the size of the threads of the nut and the head aresufficient to provide strength at least as great as the tensile strengthof the shank.

To minimize friction of the taper of the semi-cone angle of the drawingportion of the die 60 should not be substantially less than 50 and notsubstantially more than 15. This somewhat lessens the total drawingforce required but avoids any possibility of melting or plasticity fromexcessive heat. Friction also is kept low by coating the portions 51 and47 of the rod and the die interior surface with a lubricant. Thelubricant preferably forms a tought, corrosion-resistant coating, andmay be lead and also may be a polymer, such as for example, Mil-BondDraw Lubricant. The entire assembled unit 40 may be dipped in thelubricant or sprayed with the lubricant or the several parts may becoated individually. In instances where a higher initial energyabsorbing force is desired, the lubricant may be omitted from theinterior of the die and the portions 51, and applied to the portion 47,this construction providing a high initial energy absorption ratefollowed by a lower energy absorption rate.

EMBODIMENT OF FIG. 2

An energy absorbing fastener unit 80 forming an alternate embodiment ofthe invention serves to hold plate members 81 and 82 together for anyseparating force not greater than a predetermined minimum force and toabsorb a large portion of any separating force greater than thatpredetermined minimum force. The unit includes a drawable rod 84generally like the rod 44 and having an enlarged head 85, a shank 86, a.

drawable portion 87, a filleted transition portion 92 joining the headand the shank, and a tapered transition portion 91 joining the head andshank. A snap ring is adapted to be snapped over the shank 86 and aflanged split die 90 fits into a hole 93 in the member 82, the member 81having a hole 94 therein of about the same size as the hole 93. The rod84 preferably is of ductile steel and the die is substantially harder.

EMBODIMENT OF FIG. 3

An energy absorbing fastener unit forming an alternate embodiment of theinvention serves to hold plate members 101 and 102 together for anyseparating force not greater than a predetermined minimum and, when ahigher separating force occurs, to draw a drawable portion 107 of adrawable rod 104 to dissipate much of the energy of that force. The rodis like the rod 44 (FIG. 1) except as brought out below. The rodincludes a shank 106, an externally threaded head 105 much larger indiameter than the drawable portion 107, a tapered transition portion111, a filleted portion 112 joining the head to the shank and a drivingslot 113 for a screwdriver. An elongated nut 114 serves, after halves ofa flanged split die 110 are placed on the shank 106, to pull the dieagainst the member 102 and to bear against the members 101 to clamp themtightly together. The members 101 and 102 have bores 115 and 116 throughwhich the portion 107 of the rod 104 can be inserted during assembly.The shank 106 is sufficiently long that, with the head 105 to the leftof the plate member 101, the die halves can be placed on the shankcompletely to the right of the plate member 102.

EMBODIMENT OF FIG. 4

An energy absorbing fastener unit 120 forming an alternate embodiment ofthe invention holds plate members 121 and 122 together against anyseparating force not greater than a predetermined minimum separatingforce and serves to dissipate much of any separating force greater thanthat minimum force by drawing a drawable portion 127 of a drawable rod124, which is like the rod 84 (FIG. 2). The fastener unit includes onlythe rod and two halves of a flanged, split drawing die 130. The die hasan externally threaded plug 131 connected to a shank portion 132 by afrangible portion 133 formed by an external annular groove 134. The plug131 is screwed into tapped bore 135 in the member 121 and the shankportion extends into bore 136 with a flange 137 of the die bearingagainst the member 122. The rod has a head 125, a shank 126, a taperedtransition portion 128 joining'the shank to the drawable portion 127 anda fllleted, steeply sloping portion 129 joining the head and the shankand fitting into a complementary portion 138 of the die 130. The head125 and the drawable portion 127 are of the same diameter so that therod 124 may be made from rod stock by a simple turning operation formingthe shank and transition portions. The flange 137 has driving flatsthereon for screwing the plug into the tapped bore 135.

The unit 120 holds the members 121 and 122 together until a separatingforce higher than the predetermined minimum force is reached which isthe breaking strength of the frangible portion 133. Then the portion 133breaks. Preferably the braking strength of the portion is somewhathigher than the force necessary to draw the drawable portion 127 throughthe die. If so, initially there is a high instantaneous, energydissipation during breaking of the portion 133, and then there is alower, sustained absorption of energy while the portion 127 is drawn.

EMBODIMENT OF FIGS. 5 AND 6 An energy absorbing fastener unit 320forming an alternate embodiment of the invention has a bolt-likedrawable rod 324 having a long shank 326. The unit 320 secures platemembers 321 and 322 in abutment with a spacer sleeve 331 on the shankportion 326. Elongated, drawable portion 327 of the rod 324 abutsintegral die 330, and a nut 325 and a washer 332 on threaded end portion328 of the shank hold the shank under tension. The rod preferably is ofthe same material as the rod 44 (FIG. 1). The threaded portion of therod is weaker than the shank so that the drawable portion has to be moreeasily drawn than is the portion 47 of the rod 44 (FIG. 1) and the unit320 does not have a high stress ratio.

EMBODIMENT OF FIGS. 7 AND 8 An energy absorbing fastener unit 340forming an alternate embodiment of the invention is generally like theunit 320 and includes a capscrew-like, drawable rod 344 having a shank346 having a threaded portion 348, and also including an elongated,enlarged, headlike drawable portion 347 abutting a split die 350 held ina cupped bushing 343 screwed into an elongated nut 345. The nut abutsplate member 342 and the threaded portion 348 is screwed into tappedbore 349 in member 341 against which the plate member 342 is held by thefastener unit 340. The bushing has driving flats 353 and the portion 347has an Allen head socket 355.

EMBODIMENT OF FIGS. 9 AND 10 An energy absorbing fastener unit 360forming an alternate embodiment of the invention includes acapscrew-like, drawable rod 364 having a shank portion 366 having athreaded end portion 368. The rod 364 also has an elongated, drawablehead 367 which may have an Allen head socket 375 though this may beomitted. The head 367 engages washer-like integral die 370 and isscrewed into tapped bore 369 to secure members 361 and 362 together. Therod and die are generally like the rod 324 and die 330 but the portion367 and the die are rectangular in transverse cross section to produce arectangular draw.

EMBODIMENT OF FIGS. 11 AND 12 An energy absorbing fastener unit 380forming an alternate embodiment of the invention includes a drawablebolt member 384 having a reduced, flattened shank 386, a threaded endportion 388 and an elongated, enlarged drawable portion 387. Drawing diebars 390 having tapered planar drawing surfaces are adapted to draw theportion 387 in one plane only. The die bars 390 fit into square socket391 in cupped die holder 393. A nut 395 screwed on the threaded portion388 and the die holder 393 normally hold members 381 and 382 together.Upon excessive separating force being applied to the members 381 and382, the die bars 390 draw the portions 387 to absorb the energy. Theportion 388 is large and of a strength as great as that of the shank sothat the portion 387 may be large enough to secure a large drawingforce. The thread of the portion should be fine or shallow with a roundbottom and/or rolled to be favorable to a low stress riser.

EMBODIMENT OF FIGS. 13 AND 14 An energy absorbing fastener unit 400forming an alternate embodiment of the invention includes a drawableplate or bar 404 having a thinner shank 406 and a thicker, elongated,drawable head portion 407. A wedge 405 driven through a slot 409 holdsthe head portion 407 against opposed, wedge-like, drawing surfaces 411of a die 415, and the head portion is drawn when pulled through the die,a relieved or clearance portion 412 being provided at the exit of thedie. The head 7 portion may, if desired, be enlarged and the wedge 405omitted. Drawing bar inserts 403 of the die are insertable intocomplementaryholes in die holder 410 ofthe die.

EMBODIMENT OF FIGS. AND 16 An energy absorbing fastener unit 420 formingan alternate embodiment of the invention includes a fastener pin or rod424 having a shank 426 and a head 427. A head 425 on the rod serves withthe rod, a die holder 430 and a drawing die strip 432, to normally holdplate members 421 and 422 together. However, when an excessiveseparating force is applied to the members 421 and 422, the die stripdraws the portion 427 to a smaller diameter to absorb the excessiveforce. The die holder 430 is provided with a tangential entrance slot435 'to permit insertion of the die strip 432 into the die, the strip432 initially, before installation, being straight, and afterinstallation, being in the form of an annulus or sleeve. The strip is,of course, harder and more ductile than. the portion 427 and preferablyhas a hardness of greater than 60 on the Rockwell C scale, the portionpreferably being of steel having a hardness of from 50 to 55 on theRockwell C scale.

EMBODIMENT OF FIGS. 17 AND 18 An energy absorbing fastener unit 440forming an alternate embodiment of the invention includes a bolt or rod444 having a head 447, a shank 446, a threaded end portion 448 receivinga nut 445 and a washer 455, a drawing or extruding die 450 and areplaceable, drawable sleeve 452. The unit 440 normally holds platemembers 441 and 442 together, but when an excessive separating forceoccurs, the head 447 of the rod 444 pushes the sleeve 452 through thedrawing die 450 to reduce the tube and absorb the excess force. Thesleeve is freely slidable on the shank 446 so that as the sleeve iselongated by the drawing thereof, the forward end of the sleeve canslide along the rod. The head 447 is able to move freely through thedie, and rear end portion 456 of the sleeve is reduced so as to abut thehead.

EMBODIMENT OF FIGS. 19 AND 20 An energy absorbing fastener unit 460forming an alternate embodiment of the invention is like the unit 440(FIG. 24) except that the unit 460 has a splitting and rolling orcurling die 470 rather than the drawing die 450, and expands, splits androlls a tube or sleeve 472 of a ductile metal. A fastening bolt or rod464 has a shank 466 and a head 467, and a nut 465 and a washer 475 on athreaded end portion 468 tension the bolt and hold the sleeve againstthe die 470 and the die against the plate member 462 to normally holdplate members 461 and 462 together. Upon occurrence of an excessiveseparating force, the head 467 presses the sleeve to the left as viewedin FIG. 42, to expand, split and roll the sleeve to absorb the excessiveforce. The sleeve may be replaced after such an occurrence.

EMBODIMENT OF FIGS. 21 AND 22 An energy absorbing fastener unit 480forming an alternate embodiment of the invention serves to normally holdplate members 481 and 482 together and, when an excessive separatingforce is placed on the members 481 and 482 to expand and possibly splitand roll a EMBODIMENT OF FIGS. 23 AND 24 An energy absorbing fastenerunit 500 forming an alternate embodiment of the invention serves tonormally hold plate members 501 and 502 together and to absorb anyexcessive force. The unit 500 is identical with the unit 480 (FIG. 21)except that the unit 500 has an internally stepped sleeve 512 which isprogressively expanded by ahead 507 of a bolt 504 having a shank 506 ona threaded end portion 508 on which are positioned a nut 505 and awasher 511. The head 507 has a frustoconical die surface 510 to expandand possibly split and roll the tube. While the tube is shown asinternally stepped to progressively increase the amount of energyabsorbed, the tube may be stepped externally instead of internally.

EMBODIMENT OF FIGS. 25 TO 28 An energy absorbing bumper structureforming an alternate embodiment of the invention includes energyabsorbing fastener units 560 mounting a bumper 562 on ear members 561forming rigid portions of an automobile chassis frame 563. Each unit 560includes an extrudable tube 564 having an enlarged drawable portion 567welded to the bumper, a shank portion 566 threaded at 568, and a taperedtransition portion 571 fitting into a tapered, washer-like drawing die570. A nut 569 screwed onto the portion 568 draws the portion 567tightly into the die 570 and presses the die tightly against the earmember 561. Normally the tubes 564 mount the bumper 562 in the full linepositions thereof shown in FIGS. 38, 39 and 40 spaced forwardly frombody 573. However, when a collision of sufficient force occurs, thetubes 564 are extruded through the dies to dissipate the excessive forceand the bumper moves into a slot-like well 574 (FIG. 26) in the fenderand front end structure of the automobile.

EMBODIMENT OF FIGS. 29 AND 30.

' the drawable portion 684 against an extruding die 690 held by themember 682. A reverse bending die 693 and a guide roller 694 also areheld by the member 682. When excessive force occurs, the bumper pushesthe extrudable portion 687 through the drawing die 690 and pushes theshank 686 through the bending dies 691 and 693. A stripper 695straightens the rod. Thus, both extruding and triple bending occur toabsorb the excessive force.

EMBODIMENT OF FIGS. 31 TO 33 An energy absorbing structure forming analternate embodiment of the invention includes a pair of fastenerdevices 700 normally holding ears 701 against movement relative to ears702. The ears 701 are rigid with an automobiles longitudinal framemembers 703 and the ears 702 are rigid with bars 710 carrying a bumper711 of the automobile, only one of the devices 700 being shown, theother being at the other side of the frame 703. The device 700 includesa drawable rod 704 having a shank 706 and drawable portion 707 atopposite ends of the shank. The rod has tapered transition portions 708abutting flanged split dies 709 fitting closely in aligned holes 712 inthe ears. The portions 707 are identical but are reverse handed. Thatis, the rod is symmetrical. The portions 707 are tapered slightly fromsmaller at the inner ends thereof to larger at the outer ends so thatwhen excessive force occurs, both portions 707 are drawn despitemanufacturing imperfections in size or ductility of the portions 707.

Enlarged stop heads 705 are provided at each end of the rod to preventfurther drawing once both heads abut the dies. If desired, the tapers ofthe dies 709 could be different and the portions 707 untapered to causethe portions 707 to be drawn sequentially.

To take up slack, long adjustment screws 720 are screwed through tappedbores 721 in the car 702 and abut the ear 701. This permits takeup afterpartial drawing. Whenever the screws 720 are loose, a rattle will occurto indicate that they should be tightened. A guide 730 on the frame 703guides the member 710 along the frame and supports the member 710.Instead of the adjustment screws 720, spring wedges or solid wedges maybe used to separate the members 701 and What is claimed is:

1. ln an energy absorbing fastener structure, a drawable rod having acylindrical shank having a predetermined diameter, a cylindricaldrawable portion of a larger diameter at one end of the shank and a headof a larger transverse dimension than said predetermined diameter at theother end of the shank so that the strength of the head is substantiallygreater than that of the shank, the drawable portion being joined to theshank by a tapered transition portion, and a tubular member having aninternally threaded plug portion, a flanged internally tapered dieportion and a frangible portion defining the minimum cross-sectionalarea of the tubular memberjoining the plug portion and the die portion,the tubular member being positioned on the shank with the die portion insubstantial abutment with the drawable portion and with the plug portionin substantial abutment with the head.

2. The. fastener structure of claim 1 wherein the frangible portion hasa predetermined tensilestrength and the shank has a tensile strengthdifferent from said predetermined tensile strength.

1. In an energy absorbing fastener structure, a drawable rod having acylindrical shank having a predetermined diameter, a cylindricaldrawable portion of a larger diameter at one end of the shank and a headof a larger transverse dimension than said predetermined diameter at theother end of the shank so that the strength of the head is substantiallygreater than that of the shank, the drawable portion being joined to theshank by a tapered transition portion, and a tubular member having aninternally threaded plug portion, a flanged internally tapered dieportion and a frangible portion defining the minimum crosssectional areaof the tubular member joining the plug portion and the die portion, thetubular member being positioned on the shank with the die portion insubstantial abutment with the drawable portion and with the plug portionin substantial abutment with the head.
 1. In an energy absorbingfastener structure, a drawable rod having a cylindrical shank having apredetermined diameter, a cylindrical drawable portion of a largerdiameter at one end of the shank and a head of a larger transversedimension than said predetermined diameter at the other end of the shankso that the strength of the head is substantially greater than that ofthe shank, the drawable portion being joined to the shank by a taperedtransition portion, and a tubular member having an internally threadedplug portion, a flanged internally tapered die portion and a frangibleportion defining the minimum cross-sectional area of the tubular memberjoining the plug portion and the die portion, the tubular member beingpositioned on the shank with the die portion in substantial abutmentwith the drawable portion and with the plug portion in substantialabutment with the head.